The soybean (Glycine max) is a species of legume native to East Asia and widely grown for its edible bean. Varieties of soybeans are used for many purposes, including being processed into soybean meal and vegetable oil. Traditional fermented food uses of soybeans include soy sauce, fermented bean paste, natto, and tempeh, among others. Examples of non-fermented food uses include soy milk, tofu and tofu skin. Soybeans are thus a globally important crop, providing oil and protein. To maximize crop yield weeds must be controlled.
Glyphosate (N-(phosphonomethyl) glycine) is the active ingredient in glyphosate herbicides, such as ROUNDUP® brand herbicide produced by Monsanto (St. Louis, Mo.) or TOUCHDOWN® brand herbicides produced by Syngenta (Greensboro, N.C.). Typically, glyphosate is formulated as a water-soluble salt such as an ammonium, alkylamine, alkali metal or trimethylsulfonium salt. One of the most common formulations is the isopropylamine salt of glyphosate, which is the form employed in ROUNDUP® brand herbicide. TOUCHDOWN® brand herbicides utilize a formulation of either the trimethylsulfonium, potassium or diammonium salt of glyphosate.
Glyphosate is a broad spectrum herbicide that inhibits the enzyme 5-enolpyruvyl shikimate-3-phosphate synthase (EPSPS). It is conventionally applied as an aqueous solution to the foliage of plants, where it is taken up into the leaves and transported throughout the plant. Commercial formulations of glyphosate may also include one or more surfactants to facilitate penetration of the active ingredient into the plant leaves, as well as compounds to enhance rainfastness. Numerous U.S. patents disclose various formulations of glyphosate, including U.S. Pat. Nos. 4,405,531; 5,118,338; 5,196,044; 5,639,711; 5,652,197; 5,679,621; and 5,750,468.
Little success has been reported in finding natural resistance to glyphosate herbicides in plants. This is beneficial in one respect since it indicates that the likelihood of glyphosate resistant populations of weeds arising is low, but it also means that few naturally resistant desirable plant species are available. Thus, great care must be taken when applying glyphosate herbicides in the vicinity of desirable plants (such as crops, ornamentals, and grass) to avoid crop damage.